The present invention relates to a working vehicle suitable for a turf grass management working vehicle used for work such as fertilizing, chemicals spraying, lawn mowing, and the like in golf courses.
In the golf courses and parks, the working vehicle, also called turf grass management working vehicle, is used to grow turf grass. With such vehicles, various types of works such as the fertilizing, spreading topdressing, the spraying chemicals, aerating soil by injecting air, or clearing tree leaves by using a blower are conducted. The various types of works are carried out with attachments, appropriate for the types of works, mounted on a bed of the working vehicle.
In the case that a manual transmission is mounted on the working vehicle, the vehicle may be suddenly started due to an operator""s mistake upon a clutch operation, wherein wheels may become a situation of idle running to tear out turf grass. In particular, with a development of the working vehicle, it is desired not to damage the turf grass by an operation of the working vehicle since a total weight of a liquid tank reaches around 2000 kg when the tank is filled up for spraying the chemicals.
On the other hand, a technical development has occurred in which a working engine for driving a working machine which conducts each work is not mounted on the working vehicle, but an engine for driving the working vehicle drives also the working machine. For example, a working vehicle as shown in the Japanese Patent Application Publication No. 2000-145906 supplies actuating fluid as discharged from two hydraulic pumps, i.e., one hydraulic pump driven by a crank shaft of the engine and by a propeller shaft, to a hydraulic motor, thereby operating a scraper for conducting the various types of works.
In the case that the working vehicle sprays fertilizer, soil and sand, and chemicals to the turf grass, it is difficult to spray the objects such as chemicals with a uniform spray density per unit area if the spraying is carried out independently of the working vehicle speed or no constant vehicle speed is kept. That is to say, if the vehicle speed is varied under such a condition, the spraying amount per the unit area will not be uniform. Thus, caused is a bad situation that the spraying amount changes every working area.
Furthermore, there is a problem that each spraying amount per the unit area is different from that of the other soil/sand and chemicals spraying. In other words, a multi-purpose working vehicle has to take a relationship between the vehicle speed of the working vehicle and characteristics of the working machine in accordance with work content thereof. That is to say, the uniform spraying work requires to take into consideration of the change of spraying amount every work content as well as that depending on the vehicle speed.
An object of the present invention is to provide a working vehicle, which uses an engine for traveling as a power source of a working machine also, enabling various types of works to be uniformly and adequately carried out even if vehicle speed is varied as well as a smooth starting of vehicle.
The working vehicle according to the present invention has a working machine and comprises an engine, a power transmitting mechanism including an automatic transmission for transmitting a power of the engine to wheels, a drive unit connected to the engine for driving the working machine, and a control unit for controlling a transmission ratio of the automatic transmission so as to enable a rotational speed of the drive unit to change in synchronization with a vehicle speed when operating the working vehicle.
Furthermore, the working vehicle according to the present invention is characterized in that the power transmitting mechanism is provided with a torque converter connecting the engine to the automatic transmission.
In addition, the working vehicle according to the present invention is characterized in that the torque converter is provided with a lock-up clutch, and the control unit causes the lock-up clutch to be engaged when operating the working machine during traveling of the working vehicle over a predetermined travel speed.
According to these aspects of the present invention, the torque converter is operated between a starting speed and a predetermined travel speed to obtain a large driving force and absorb a rotational difference between the engine and the automatic transmission, so that a smooth starting of vehicle becomes possible. As a result, it can be prevented that wheels tear out turf grass due to an idle running of the wheels, so that the turf grass is not damaged by the operation of the working vehicle. Also, the control unit causes the lock-up clutch to be engaged when operating the working machine during traveling of the working vehicle with a predetermined travel speed or above, so that slipping of the torque converter can be prevented.
Furthermore, the working vehicle according to the present invention is characterized in that the working vehicle is provided with a plurality of work modes, and the control unit controls the automatic transmission based on a relationship between the rotational speed of the drive unit and the vehicle speed, wherein the relationship corresponds with any work mode selected from the plurality of ones.
According to these aspects of the present invention, if the work mode is appropriately selected in accordance with the work content, the transmission ratio of the automatic transmission can be set in such a way that there is a predetermined interrelationship between the work amount and the vehicle speed. Therefore, the working vehicle can be driven corresponding with the vehicle speed in accordance with the work content, that is, the fertilizer, sand, and chemicals can be uniformly spread. In a word, the present invention enables the working vehicle to easily deal with a various type of works by one machine through changing the work mode.
In addition, the working vehicle according to the present invention is characterized in that the automatic transmission is a continuously variable transmission comprising a primary pulley for inputting a rotational speed of the engine, a secondary pulley for outputting the rotation to the wheels, and a belt for connecting between the primary pulley and the secondary pulley.
Thereby, a shift control can be smoothly and steplessly conducted.
Also, the working vehicle according to the present invention is characterized in that the control unit controls the transmission ratio of the automatic transmission so as to enable the rotational speed of the drive unit to be substantially proportional to a change of the vehicle speed in at least predetermined range of the vehicle speed.